From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752631AbbANNGz (ORCPT ); Wed, 14 Jan 2015 08:06:55 -0500 Received: from cantor2.suse.de ([195.135.220.15]:57358 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751749AbbANNGy (ORCPT ); Wed, 14 Jan 2015 08:06:54 -0500 Date: Wed, 14 Jan 2015 14:06:52 +0100 Message-ID: From: Takashi Iwai To: Lars-Peter Clausen Cc: Mark Brown , "alsa-devel@alsa-project.org" , "Wang, Jiada (ESD)" , "linux-kernel@vger.kernel.org" , "lgirdwood@gmail.com" , "Frkuska, Joshua" Subject: Re: [alsa-devel] unload Audio drivers while playback stream is active case kernel crash In-Reply-To: <54B6679F.1030706@metafoo.de> References: <857E9EDCA6C0904DB3357321AA9123EB0108B66919@NA-MBX-01.mgc.mentorg.com> <20150113215412.GS4160@sirena.org.uk> <54B625A8.8090406@metafoo.de> <54B63E4F.2010506@metafoo.de> <20150114120228.GT4160@sirena.org.uk> <54B6679F.1030706@metafoo.de> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.4 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At Wed, 14 Jan 2015 13:57:03 +0100, Lars-Peter Clausen wrote: > > On 01/14/2015 01:02 PM, Mark Brown wrote: > [...] > >>> I don't think that we need to prevent module unload when a stream is active. > >>> From a framework point of view is not different from hot-unplug. I don't > >>> see a reason why we'd jump through hoops to actively forbid removing the > >>> module once it works just fine. > > > >> Well, the module unload means a more drastic cleanup. Even if you > >> unbind, the code and data are still there while module unload may > >> clean them up all. > > > >> Above all, disallowing the module unload while using is the common > >> behavior of any other drivers. Why do we have to be a rebel against > >> all civil manner? :) > > > > That's not true for everything and for ASoC I'd tend to assume that the > > user knows what they're doing and has a good reason for it; it's > > certainly something that can be helpful in development. > > > My personal opinion on this is that disallowing module removal while a > driver registered by the module when is in use, while there is no technical > reason to do so, is a anti-feature. Whether in ALSA or elsewhere. > > But looking at the source it seems that this is a core feature of ALSA and > at least for the card module itself it will do the ref-counting when a > stream is started/stopped. And we even support setting the owner of a card > in ASoC. It's just that pretty much no ASoC card driver bothers to set the > owner field in the snd_soc_card struct. So this particular problem can be > fixed by updating the imx-wm8962 driver to set the owner field. Right, and that's what I wanted to hear. My concern was about the missing piece in the existing core part. The rest of hotplug fix is of course a thing to be done in anyway. Takashi